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Irrigation expert drops water knowledge on green thumbs

Irrigation expert drops water knowledge on green thumbs
David Bainbridge, retired professor and author of "Gardening with Less Water," discussed efficient irrigation systems Tuesday night at Neighborhood Congregational Church. (Courtesy of David Bainbridge)

Terra cotta planters. Recycled bottles. Nylon rope.

They're all drought-resilient materials that retired professor and author David Bainbridge recommended for watering a garden when he spoke Tuesday night at Neighborhood Congregational Church in Laguna Beach.

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Clay pots maintain good soil moisture. And wettable fabric or rope can carry water from a reservoir — a recycled bottle, for instance — to the roots of a plant.

"A change is going to come," Bainbridge said to audience members from Transition Laguna, a grass-roots organization that meets monthly to discuss such topics as edible gardens, water and energy conservation and emergency preparedness and also holds workshops. "The goal is to use less water, and that can be done up to 90% in a garden."

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San Diego-based Bainbridge, who has a PhD in ecology, has traveled the world to discover efficient irrigation systems.

He has written several books, including "Gardening with Less Water," an illustrated manual offering simple, inexpensive and low-tech techniques for cutting garden-watering consumption by up to 90%.

"There are pioneers in every field, and David is one of the pioneers in sustainability," said Chris Prelitz, president of Transition Laguna and owner of Laguna Beach-based construction company Preltiz Design + Build, who has known Bainbridge for 25 years and invited him to speak. "He's like an encyclopedia when it comes to the environment. He's done what he can for us to be better to nature."

The instructions in his latest book, Bainbridge said, are based on the indigenous solutions he learned: Deliver water directly to a plant's roots to limit evaporation and go beyond basic irrigation efficiency.

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According to the U.S. Geological Survey, the average person uses 80 to 100 gallons of water per day. Outdoor watering uses about 2 gallons per minute, depending on the force of the outdoor faucet.

And the Environmental Protection Agency estimates that as much as 50% of the water used for garden irrigation is wasted because of evaporation or runoff.

One way to save water is the use of the olla, or terra cotta pot, Bainbridge said, explaining that the technique borrows from the ancient form of localized plant irrigation.

Ollas, pronounced oyas, are positioned in the ground, with just their narrow neck showing, and they are to be refilled with water every five to 10 days. Once nearby plants are established, their roots grow toward the water source, and over time, the roots attach themselves to the outside of the olla and draw water out as they need it, Bainbridge said.

Ollas come in three sizes and are designed to fit in any growing plan, including vegetable and flower gardens as well as raised beds and rooftop layouts.

Plants, Bainbridge said, take what they need, and clay pots hold in soil moisture.

The pots cost $24.95 to $39.95 through water-conserving business GrowOya.com. Bainbridge said porous terra cotta nursery pots can also be used, but the holes must be plugged with a rubber stopper or epoxy.

Bainbridge also talked about wick irrigation, which is a low-cost watering alternative. Wicks are a wettable fabric or rope that can carry water from a reservoir to the roots of the plant. Bainbridge said the simplist form can be done with recycled bottles and washed solid braid made from 100% nylon or polyester ropes.

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This form of irrigation, he said, is best for African violets since the plant's leaves are very sensitive to wet and cold conditions.

To deliver irrigation water to a deep root zone, Bainbridge said, consider deep pipe irrigation using a pipe, bamboo or plant container. The pipe should be set on the uphill side on a slope and filled from a jug or hose or fitted with a rainwater catcher.

His fourth recommendation is use of a porous hose, but he said this irrigation method is not as efficient though it is simple. The hose is made of recycled rubber material and has several tiny holes. Under pressure, water sweats along the full length of the line and waters flower beds, potted plants and vegetable gardens.

Which method is best?

"It all depends," Bainbridge said. "Many gardens could benefit from them all. I would suggest to start with ollas first. Just try it. It has made a difference in my garden."

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Kathleen Luppi, kathleen.luppi@latimes.com

Twitter: @KathleenLuppi

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